Method and apparatus for selecting inlets of a multiple inlet FAIMS

Abstract

An ion introduction system for selecting ions from one of two separate ionization sources of ions is provided. The system includes a plate having a hole formed therethrough, the plate for being disposed adjacent an ion introduction region of a gas phase ion analyzer such that the hole is selectively movable between a first location in which the hole is adjacent to a first ionization source of ions for supporting introduction of ions from the first ionization source of ions into the gas phase ion analyzer, and a second location in which the hole is adjacent to a second ionization source of ions for supporting introduction of ions from the second ionization source of ions into the gas phase ion analyzer. The system also includes a drive mechanism for driving the plate between a first position in which the hole is at the first location and a second position in which the hole is at the second location.

1. An apparatus for separating ions, comprising:
 a first electrode; 
 a second electrode disposed in a spaced-apart relationship with the first electrode, a space between the first electrode and the second electrode defining a FAIMS analyzer region therebetween, the FAIMS analyzer region in fluid communication with an ion outlet orifice; 
 a first ion inlet orifice defined within a first portion of the first electrode, the first ion inlet orifice spaced-apart from the ion outlet orifice by a first distance, such that ions introduced via the first ion inlet orifice travel the first distance through the FAIMS analyzer region between the first ion inlet orifice and the ion outlet orifice; 
 a second ion inlet orifice defined within a second portion of the first electrode, the second ion inlet orifice spaced-apart from the ion outlet orifice by a second distance that is shorter than the first distance, such that ions introduced via the second ion inlet orifice travel the second distance between the second ion inlet orifice and the ion outlet orifice; and, 
 an ion inlet orifice selector comprising a selector electrode having an opening defined therethrough, the selector electrode moveable between a first position in which the opening is aligned with the first ion inlet orifice for supporting introduction of a flow of ions into the FAIMS analyzer region via the first ion inlet orifice and a second position in which the opening is aligned with the second ion inlet orifice for supporting introduction of a flow of ions via the second ion inlet orifice. 
 
     
     
       2. An apparatus according to  claim 1 , comprising a power supply for applying an asymmetric waveform voltage and a direct current compensation voltage between the first electrode and the second electrode, to establish an electric field within the analyzer region for effecting a FAIMS-based separation of ions. 
     
     
       3. An apparatus according to  claim 1 , wherein the second distance is selected to provide an average ion flow path through the analyzer region that is sufficiently short to support simultaneous transmission of plural types of ions contained in a mixture of ions introduced via the second ion inlet orifice. 
     
     
       4. An apparatus according to  claim 3 , wherein the first distance is selected to provide an average ion flow path through the analyzer region that is sufficiently long to support at least partial separation of a first type of ion contained in a mixture of ions introduced via the first ion inlet orifice from a second type of ion contained in the same mixture. 
     
     
       5. An apparatus according to  claim 1 , wherein the ion inlet orifice selector comprises a motor rotationally coupled to the ion inlet selector, the motor for actuating the selector electrode between the first position and the second position. 
     
     
       6. An apparatus according to  claim 5 , wherein the ion inlet orifice selector comprises a drive shaft disposed between the motor and the selector electrode, the drive shaft for transferring rotational motion of the motor to the selector electrode. 
     
     
       7. An apparatus according to  claim 1 , comprising a first ionization source disposed adjacent to the first ion inlet orifice for providing a flow of analyte ions produced from a sample material for introduction via the first ion inlet orifice. 
     
     
       8. An apparatus according to  claim 7 , comprising a second ionization source disposed adjacent to the second ion inlet orifice for providing a flow of ions produced from a calibration compound for introduction via the second ion inlet orifice. 
     
     
       9. An apparatus according to  claim 1 , comprising a curtain plate electrode disposed between the selector electrode and the first electrode, the curtain plate electrode comprising a first curtain gas orifice for being aligned with the first ion inlet orifice when in an assembled condition, and comprising a second curtain gas orifice for being aligned with the second ion inlet orifice when in an assembled condition. 
     
     
       10. An apparatus according to  claim 1 , comprising an electrically insulating member mounted to the selector electrode and extending toward the first electrode a distance sufficient to form a substantially gas-tight seal between the electrically insulating member and one of the first portion of the first electrode and the second portion of the first electrode. 
     
     
       11. An apparatus according to  claim 10 , wherein the electrically insulating member is dimensioned for forming a substantially gas tight seal with the first electrode about either one of the first ion inlet orifice and the second ion inlet orifice, but not during a same overlapping period of time. 
     
     
       12. An apparatus according to  claim 11 , wherein the electrically insulating member is mounted to the selector electrode such that when one of the first ion inlet orifice and the second ion inlet orifice is aligned with the electrically insulating member, the other one of the first ion inlet orifice and the second ion inlet orifice is aligned with the opening through the selector electrode. 
     
     
       13. An apparatus according to  claim 12  wherein the selector electrode is electrically insulated from the first electrode and forms a substantially gas-tight seal with the first electrode about the first and second portions thereof, so as to define a curtain gas region proximate the first ion inlet orifice and the second ion inlet orifice. 
     
     
       14. A method for separating ions, comprising:
 providing a FAIMS analyzer region in fluid communication with an ion detector; 
 providing a first ionization source in communication with a sample material including a precursor of an ion type of interest; 
 providing a second ionization source in communication with a sample material including the precursor of the ion type of interest; 
 using the first ionization source, producing a mixture of ions comprising different types of ions including the ion type of interest; 
 during a first period of time, directing the ions from the first ionization source along a path of a first length through the FAIMS analyzer region, the first length being sufficient to effect at least a partial separation of the ion type of interest from other types of ions in the mixture; 
 using the ion detector, detecting ions after the ions have traveled the first length; 
 using the second ionization source, producing a mixture of ions comprising different types of ions including the ion type of interest; 
 during a second period of time not overlapping with the first period of time, directing the ions from the second ionization source along a path of a second length through the FAIMS analyzer region, the second length being insufficient to effect a separation of the ion type of interest from other types of ions in the mixture to a same extent as occurs along the path of the first length; 
 using the ion detector, detecting ions after the ions have traveled the second length. 
 
     
     
       15. A method according to  claim 14 , wherein more of the different types of ions are detected by the detector after the ions have traveled the path of a second length relative to a number of the different types of ions that are detected by the detector after the ions have traveled the path of a first length. 
     
     
       16. A method according to  claim 14 , wherein directing the ions from the first ionization source along a path of a first length through the FAIMS analyzer region comprises aligning an opening defined within a selector electrode with a first ion inlet into the FAIMS analyzer region. 
     
     
       17. A method according to  claim 16 , wherein directing the ions from the second ionization source along a path of a second length through the FAIMS analyzer region comprises aligning the opening defined within the selector electrode with a second ion inlet into the FAIMS analyzer region. 
     
     
       18. A method according to  claim 17 , wherein each one of the first ionization source and the second ionization source produce ions during the first period of time and the second period of time. 
     
     
       19. A method according to  claim 18 , comprising during a third period of time, moving the selector electrode from a first condition in which the opening is aligned with the first ion inlet into the FAIMS analyzer region to a second condition in which the opening is aligned with the second ion inlet into the FAIMS analyzer region. 
     
     
       20. A method according to  claim 19 , wherein the third period of time is short relative to both the first period of time and the second period of time. 
     
     
       21. A method according to  claim 19 , wherein moving the selector electrode comprises rotating the selector electrode. 
     
     
       22. A method according to  claim 19 , wherein the ion detector comprises a mass spectrometer, and wherein the mixture of ions produced by the second ionization source includes ions of a compound for calibrating the mass spectrometer. 
     
     
       23. A method for separating ions, comprising:
 providing a FAIMS analyzer region in fluid communication with an ion detector; 
 introducing a mixture of different types of ions including an ion type of interest into the analyzer region via a first ion inlet orifice; 
 selectively transmitting the ion type of interest along a first distance through the FAIMS analyzer region from the first ion inlet to the ion detector; 
 introducing ions of a calibration compound into the FAIMS analyzer region via a second ion inlet orifice, the second ion inlet orifice positioned for use in calibration; 
 transmitting the ions of a calibration compound along a second distance shorter than the first distance through the FAIMS analyzer region from the second ion inlet to the ion detector; and, 
 in dependence upon a response of the ion detector to the ions of a calibration compound, modifying at least one operational parameter of the ion detector. 
 
     
     
       24. A method according to  claim 23 , comprising providing a first ionization source in communication with a sample material including a precursor of the ion type of interest. 
     
     
       25. A method according to  claim 24 , wherein introducing a mixture of different types of ions comprises using the first ionization source to produce the mixture of ions comprising different types of ions including the ion type of interest and, during a first period of time, aligning an opening of a selector electrode between the first ionization source and a first ion inlet into the FAIMS analyzer region and selectively transmitting the ion type of interest through the analyzer region. 
     
     
       26. A method according to  claim 25 , comprising providing a second ionization source in communication with a material including a precursor of the ions of the calibration compound. 
     
     
       27. A method according to  claim 26 , wherein introducing ions of a calibration compound comprises using the second ionization source to produce the ions of the calibration compound and, during a second period of time not overlapping with the first period of time, aligning the opening of the selector electrode between the second ionization source and a second ion inlet into the FAIMS analyzer region and selectively transmitting the ions of the calibration compound through the analyzer region. 
     
     
       28. A method according to  claim 27 , comprising determining a measured mass-to-charge ratio of the ions of a calibration compound and in dependence upon a difference between the determined mass-to-charge ratio of the ions of a calibration compound and a known mass-to-charge ratio of the ions of a calibration compound, producing a revised mass-scale. 
     
     
       29. A method according to  claim 28 , comprising detecting the ion type of interest using the mass spectrometer and determining a mass-to-charge ratio of the ion type of interest based on the revised mass-scale. 
     
     
       30. A method for separating ions, comprising:
 providing a FAIMS analyzer region in fluid communication with a mass spectrometric ion detector; 
 providing a first ionization source in communication with a sample material including a precursor of an ion type of interest; 
 providing a second ionization source in communication with a material including a precursor of a calibration compound ion; 
 using the first ionization source, producing a mixture of ions comprising different types of ions including the ion type of interest; 
 using the second ionization source, producing calibration compound ions from the precursor of the calibration compound ion; 
 during a first period of time, aligning an opening of a selector electrode between the second ionization source and a first ion inlet into the FAIMS analyzer region; 
 during the first period of time, directing the calibration compound ions from the second ionization source into the FAIMS analyzer region and transmitting the calibration compound ions along a first distance through the FAIMS analyzer region from the first ion inlet to the mass spectrometric ion detector; 
 detecting the calibration compound ions and determining the mass-to-charge ratio of the calibration compound ions; 
 calibrating the mass-scale in dependence upon a difference between the determined mass-to-charge ratio of the calibration compound ions and an expected mass-to-charge ratio of the calibration compound ions; 
 during a second period of tune not overlapping with the first period of time, aligning the opening of the selector electrode between the first ionization source and a second ion inlet into the FAIMS analyzer region; 
 during the second period of time, directing the ions from the first ionization source into the FAIMS analyzer region and selectively transmitting the ion type of interest along a second distance longer than the first distance through the FAIMS analyzer region from the second ion inlet to the mass spectrometric ion detector; and, 
 detecting the ion type of interest using the mass spectrometric ion detector and determining the mass-to-charge ratio of the ion type of interest.